1. Field of the Invention
The present invention relates to an image processing method and image processing apparatus. Particularly, the present invention relates to an image processing method and image processing apparatus which man-machine-interactively select a partial area of an image displayed on a screen and cut out or process the image in the selected area.
2. Description of the Related Art
In cutting out a part of an image displayed on a screen and compositing it with another image, a known technique is used to shade off the edge of the cut-out area to suppress jaggedness of the image edge. For example, Japanese Patent Publication Laid-Open No. 4-340671 proposes a technique of suppressing jaggedness upon image composition by shading off both sides of the boundary of a mask image (by uniformly allocating the shade-off inside and outside of the image).
The technique of shading off the boundary part of a mask image in cut-out image composition is very effective for suppression of jaggedness.
In the prior art, however, background pixels around the boundary are subjected to shade-off processing upon shading off the edge periphery. This processing may make transparent background pixels translucent. As a result, the processed part is noticeable.
As a psychological aspect of an operator who should specify an image cut-out area man-machine-interactively, she/he tends to set an area including the cut-out target image as much as possible. As a result, the cut-out boundary part often contains the background image. If the periphery of the boundary part shades off in this state, the background image area extends, resulting in a poor image quality in the boundary area.
If an area is partially deleted from an image with shading off near the edge, the contrast of the edge part is degraded. The edge of the deletion target area that must be transparent becomes translucent. Hence, it is impossible to completely delete the desired part.
Additionally, the operator feels stress in editing and finely adjusting the boundary part of an image cut-out area by, e.g., man-machine-interactively editing the outline point of each pixel or painting the mask edge.